| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.flink.runtime.leaderretrieval; |
| |
| import org.apache.flink.runtime.leaderelection.LeaderInformation; |
| import org.apache.flink.runtime.rpc.FatalErrorHandler; |
| import org.apache.flink.util.Preconditions; |
| |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import javax.annotation.Nullable; |
| import javax.annotation.concurrent.GuardedBy; |
| |
| import java.util.Objects; |
| import java.util.UUID; |
| |
| import static org.apache.flink.util.Preconditions.checkNotNull; |
| |
| /** |
| * The counterpart to the {@link |
| * org.apache.flink.runtime.leaderelection.DefaultLeaderElectionService}. Composed with different |
| * {@link LeaderRetrievalDriver}, we could retrieve the leader information from different storage. |
| * The leader address as well as the current leader session ID will be retrieved from {@link |
| * LeaderRetrievalDriver}. |
| */ |
| public class DefaultLeaderRetrievalService |
| implements LeaderRetrievalService, LeaderRetrievalEventHandler { |
| private static final Logger LOG = LoggerFactory.getLogger(DefaultLeaderRetrievalService.class); |
| |
| private final Object lock = new Object(); |
| |
| private final LeaderRetrievalDriverFactory leaderRetrievalDriverFactory; |
| |
| @GuardedBy("lock") |
| @Nullable |
| private String lastLeaderAddress; |
| |
| @GuardedBy("lock") |
| @Nullable |
| private UUID lastLeaderSessionID; |
| |
| @GuardedBy("lock") |
| private volatile boolean running; |
| |
| /** Listener which will be notified about leader changes. */ |
| private volatile LeaderRetrievalListener leaderListener; |
| |
| private LeaderRetrievalDriver leaderRetrievalDriver; |
| |
| /** |
| * Creates a default leader retrieval service with specified {@link |
| * LeaderRetrievalDriverFactory}. |
| * |
| * @param leaderRetrievalDriverFactory {@link LeaderRetrievalDriverFactory} used for creating |
| * {@link LeaderRetrievalDriver}. |
| */ |
| public DefaultLeaderRetrievalService( |
| LeaderRetrievalDriverFactory leaderRetrievalDriverFactory) { |
| this.leaderRetrievalDriverFactory = checkNotNull(leaderRetrievalDriverFactory); |
| |
| this.lastLeaderAddress = null; |
| this.lastLeaderSessionID = null; |
| |
| this.leaderRetrievalDriver = null; |
| |
| running = false; |
| } |
| |
| @Override |
| public void start(LeaderRetrievalListener listener) throws Exception { |
| checkNotNull(listener, "Listener must not be null."); |
| Preconditions.checkState( |
| leaderListener == null, |
| "DefaultLeaderRetrievalService can " + "only be started once."); |
| |
| synchronized (lock) { |
| leaderListener = listener; |
| leaderRetrievalDriver = |
| leaderRetrievalDriverFactory.createLeaderRetrievalDriver( |
| this, new LeaderRetrievalFatalErrorHandler()); |
| LOG.info("Starting DefaultLeaderRetrievalService with {}.", leaderRetrievalDriver); |
| |
| running = true; |
| } |
| } |
| |
| @Override |
| public void stop() throws Exception { |
| LOG.info("Stopping DefaultLeaderRetrievalService."); |
| |
| synchronized (lock) { |
| if (!running) { |
| return; |
| } |
| running = false; |
| } |
| |
| leaderRetrievalDriver.close(); |
| } |
| |
| /** |
| * Called by specific {@link LeaderRetrievalDriver} to notify leader address. |
| * |
| * @param leaderInformation new notified leader information address. The exception will be |
| * handled by leader listener. |
| */ |
| @Override |
| @GuardedBy("lock") |
| public void notifyLeaderAddress(LeaderInformation leaderInformation) { |
| final UUID newLeaderSessionID = leaderInformation.getLeaderSessionID(); |
| final String newLeaderAddress = leaderInformation.getLeaderAddress(); |
| synchronized (lock) { |
| if (running) { |
| if (!Objects.equals(newLeaderAddress, lastLeaderAddress) |
| || !Objects.equals(newLeaderSessionID, lastLeaderSessionID)) { |
| if (LOG.isDebugEnabled()) { |
| if (newLeaderAddress == null && newLeaderSessionID == null) { |
| LOG.debug( |
| "Leader information was lost: The listener will be notified accordingly."); |
| } else { |
| LOG.debug( |
| "New leader information: Leader={}, session ID={}.", |
| newLeaderAddress, |
| newLeaderSessionID); |
| } |
| } |
| |
| lastLeaderAddress = newLeaderAddress; |
| lastLeaderSessionID = newLeaderSessionID; |
| |
| // Notify the listener only when the leader is truly changed. |
| leaderListener.notifyLeaderAddress(newLeaderAddress, newLeaderSessionID); |
| } |
| } else { |
| if (LOG.isDebugEnabled()) { |
| LOG.debug( |
| "Ignoring notification since the {} has already been closed.", |
| leaderRetrievalDriver); |
| } |
| } |
| } |
| } |
| |
| private class LeaderRetrievalFatalErrorHandler implements FatalErrorHandler { |
| |
| @Override |
| public void onFatalError(Throwable throwable) { |
| synchronized (lock) { |
| if (!running) { |
| if (LOG.isDebugEnabled()) { |
| LOG.debug( |
| "Ignoring error notification since the service has been stopped."); |
| } |
| return; |
| } |
| |
| if (throwable instanceof LeaderRetrievalException) { |
| leaderListener.handleError((LeaderRetrievalException) throwable); |
| } else { |
| leaderListener.handleError(new LeaderRetrievalException(throwable)); |
| } |
| } |
| } |
| } |
| } |